drivers/video/acornfb.c: use __free_reserved_page() to simplify the code

Use __free_reserved_page() to simplify the code in the others.

Signed-off-by: Xishi Qiu <qiuxishi@huawei.com>
Cc: Jean-Christophe Plagniol-Villard <plagnioj@jcrosoft.com>
Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>